native.Bitmap: when bitmapData == null, it should clear its graphic.
native.Bitmap: when bitmapData == null, it should clear its graphic.

madrazo/nme,haxenme/nme,haxenme/nme,thomasuster/NME,thomasuster/NME,haxenme/nme,thomasuster/NME,madrazo/nme,madrazo/nme,madrazo/nme,madrazo/nme,thomasuster/NME,thomasuster/NME,haxenme/nme,madrazo/nme,haxenme/nme,thomasuster/NME